Fix restoring orientation in onBack

app/src/main/java/org/schabi/newpipe/fragments/detail/VideoDetailFragment.java

@@ -742,20 +742,19 @@ public boolean onBackPressed() {
                 && player.getPlayQueue() != null
                 && player.videoPlayerSelected()
                 && player.getPlayQueue().previous()) {
-            return true;
+            return true; // no code here, as previous() was used in the if
         }
+
         // That means that we are on the start of the stack,
-        // return false to let the MainActivity handle the onBack
         if (stack.size() <= 1) {
             restoreDefaultOrientation();
-
-            return false;
+            return false; // let MainActivity handle the onBack (e.g. to minimize the mini player)
         }
+
         // Remove top
         stack.pop();
         // Get stack item from the new top
-        assert stack.peek() != null;
-        setupFromHistoryItem(stack.peek());
+        setupFromHistoryItem(Objects.requireNonNull(stack.peek()));
 
         return true;
     }
@@ -1432,17 +1431,15 @@ public void onReceive(final Context context, final Intent intent) {
     //////////////////////////////////////////////////////////////////////////*/
 
     private void restoreDefaultOrientation() {
-        if (!isPlayerAvailable() || !player.videoPlayerSelected() || activity == null) {
-            return;
+        if (isPlayerAvailable() && player.videoPlayerSelected()) {
+            toggleFullscreenIfInFullscreenMode();
         }
 
-        toggleFullscreenIfInFullscreenMode();
-
         // This will show systemUI and pause the player.
         // User can tap on Play button and video will be in fullscreen mode again
         // Note for tablet: trying to avoid orientation changes since it's not easy
         // to physically rotate the tablet every time
-        if (!DeviceUtils.isTablet(activity)) {
+        if (activity != null && !DeviceUtils.isTablet(activity)) {
             activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
         }
     }